Samarangana Sutradhara -

Mainstream historians argue that the Samarangana Sutradhara is a —a theoretical, idealized treatise, not a practical manual. Just as modern textbooks contain problem diagrams that are not meant to be built, Bhoja’s mercury engines are thought to be "thought experiments." Furthermore, no archaeological evidence of a mercury-powered Vimana has ever been found.

If the first 60 chapters are remarkable, Chapter 31 of the Samarangana Sutradhara is breathtaking. Titled "Vimana Yantra Prakarana" (The Section on Vimana Machines), it contains 230 verses dedicated solely to flying machines. samarangana sutradhara